It varies dramatically. It varies across subsector, on the street, in a massage parlour, in an escort agency. It varies geographically.
I can say that if you are working for somebody else, you can give anywhere from 5% or 10% up to, more commonly, 50% or 60%, and in situations that I would call largely exploitative, it could be as much as 100%. Often it's dependent upon what services you're getting in return, so if an escort agency is providing a driver, a place to work, and paying for your ads, you're going to be paying more than for an escort agency that, for example, is just running an ad for you.